This invention relates to a device for the closure of incisions at the conclusion of many typical surgical procedures. Such closures can involve the rejoining of a wide variety of tissue types and bones, such as the rib cage, fascia, muscle, skin and fat. Primary objectives of these closure procedures are to effect rapid and proper healing with a minimum of discomfort and scarring and to ensure that the wound remains securely closed. A related objective is that the closure not interfere with subsequent bandages and change of dressing.
Closure generally involves joining various layers of tissue, each in a special and correct manner. For instance, in abdominal surgery, the severed peritoneum layer must be joined, followed by the layers of muscle, fascia, fat and skin. Additionally, retention sutures which pass through all layers may be used or required as insurance that the closure will not open. To accomplish these sutured closures typical materials include silk, gut in a wide variety of synthetics including Dacron .RTM., Teflon .RTM., and various new disposable materials. Depending upon the strength required, the material may be monofilament or braided and the caliber may be varied. Also, there are metal sutures which are usually made from non-reactive stainless steel. Each material has characteristics which make its use appropriate for a specific purpose.
In all these techniques an important consideration is scar formation, the manner in which the human body reacts to suture materials which behave, for the most part, as foreign bodies and cause the body's defense mechanisms to seal them off with connective tissue. When the body's reaction is greater, more scar tissue will be formed.
Obviously, sutures cannot be passed without a delivery system which for these sutures consists of a large assortment of needles. Each type of needle is designed to provide a particular function, such as ease of handling, ease of passage, ease of release, minimal trauma, etc. The surgeon will generally either thread a needle or use pre-threaded suture-needle combinations in secondary instruments such as suture holders.
Wound closure is thus a major concern among surgeons and among the primary objectives of wound closure are: (a) to minimize time required to close, (b) to reduce surgeon fatigue and patient anesthesia time, (c) to reduce tissue trauma and accelerate wound healing, (d) to minimize blood loss, (e) to achieve optimum cosmetic results, and (f) to control and reduce overall costs.
These objectives have led to the development of a relatively new method of closure, namely, joining adjacent tissue with metal staples delivered and secured by a staple gun. These metal staples which have partially replaced traditional suture techniques, have become popular for both external and internal closures, including joining cut ends of blood vessels, hollow organs and various layers of tissue within the body. Dozens of stapling devices for surgery have been developed by Americans and others, especially workers in the Soviet Union.
One aspect of virtually all of these known stapling devices is the characteristic way in which they function and the use of bendable but nonresilient metal staples. Force is applied to change the initially open, generally U-shaped configuration of each metal staple to a final, closed configuration, so that the staple will hold two adjacent edges of tissue together. The staple devices are held and operated by the surgeon's hand, with force applied either manually by the surgeon or by a power-assisted manual force incorporated into the stapler. The force required to bend or crush the ends of the nonelastic metal staples is substantial, and is typically applied by a driver which drives each staple into position and then forcibly bends the legs of the staple. Once placed, the staples cannot be removed without the use of a separate device which forcibly returns the staple to its generally open configuration, so that removal is possible without tearing the tissue.
Applicant has previously invented a surgical stapler which utilizes a unique delivery system which provides a mode of increased control and includes provision for turning the staple generally normal to the plane of a stack of staples which are stacked as in a conventional paper stapler, to provide a more efficient and space-saving surgical stapler. The subject matter of such a stapler is disclosed in U.S. Pat. No. 4,691,853 issued Sept. 8, 1987. Practical experience with a working model of the invention described in U.S. Pat. No. 4,691,853 has led to several improvements described herein which will be perceived as advantages by the intended users, i.e. surgical personnel.
The improvements include advancing the staple within the case so that the rotation occurs within the housing, setting the staple at the end of the forward stroke, releasing the staple on the return stroke, provision for a varying mechanical advantage to accommodate the staple advance at a reasonable hand force level, and provision for adjusting the amount of tissue which is drawn up or approximated within the perimeter of the formed staple. This application, however, retains the original features in U.S. Pat. No. 4,691,853 of rotating the staple and stripping the lower anvil on the forward stroke using the surface of the former to restrain the staple.